Such a facility for combusting carbonaceous residues is described in Patent FR 2 850 156.
This facility includes a reactor for reducing oxides, a first cyclone, exchangers for flue gas heat recovery, a reactor for oxidizing oxides, a second cyclone, exchangers for controlling temperature of the circulating oxides, in which circulates an oxide which is reduced and then oxidized in each of both reactors. According to this prior art, the solid combustible material is milled before entering the oxide reduction reactor. The oxides are reduced by first of all having them in contact with the fuel which reacts with the oxygen released by the oxide and then oxidized by contact with air which regenerates the oxide. The reduced: size of the solid fuel particles allows more complete and faster combustion and production of nearly 100% of fly ash.
This type of facility for combustion of carbonaceous solid materials operating at atmospheric pressure with integrated capture of carbon dioxide does not require any prior air separation. Because of the simplicity and the compactness of this system the costs of capturing carbon dioxide may be reduced while providing production of steam for generating electricity.
The solid particles at the outlet of the first cyclone associated with the reduction reactor, consisting of metal oxide particles and of carbonaceous residues, pass through a siphon and are then directed towards a device for removing the carbonaceous residue.
This removal device is fluidized by steam. With this fluidization, the fine and light particles such as the carbonaceous residue may be separated and re-introduced into the reduction reactor, while the denser and larger metal oxide particles are transferred towards the oxidation reactor.
This removal device which is a separator, contains an internal baffle formed with a wall integral with the roof of the separator and leaving a flow space in the bottom of the latter and which forms two compartments on the passage of fluidized solids with a pressure seal provided by the height of the fluidized solids, between the two compartments. The fluidization of each compartment is independently controlled by two steam inlets, in order to obtain the desired velocity field for separating the oxides and the carbonaceous residues in the first compartment as well as the transfer of the oxides into the second compartment. Above the first compartment, a vent brings the carbonaceous residues carried off by steam back towards the reduction reactor.
This separator is a carbon barrier in the facility, essential for capturing carbon dioxide which is a greenhouse gas which should be subject to emission restrictions.